Fiber optic cable location system and method

ABSTRACT

In some examples, fiber optic cable location may include transmitting a coherent laser pulse into a device under test (DUT). Based on an analysis of reflected light resulting from the transmitted coherent laser pulse, changes in intensity of the reflected light caused by a plurality of signals directed towards the DUT may be determined. Further, based on the changes in intensity of the reflected light, a location of the DUT may be determined.

PRIORITY

This application is a Continuation of commonly assigned U.S. patentapplication Ser. No. 16/388,536, filed Apr. 18, 2019, which claimspriority under 35 U.S.C. 119(a)-(d) to European patent applicationnumber 19305402.0, having a filing date of Mar. 28, 2019, thedisclosures of which are hereby incorporated by reference in theirentireties.

BACKGROUND

A fiber optic cable may include one or more optical fibers. The opticalfibers may transmit light from a source to a destination. The opticalfibers may be disposed in a protective layer that may be formed ofplastic or another suitable material. Once the fiber optic cable isplaced at a site, the cable may need to be located, for example, formaintenance, service connection, etc.

BRIEF DESCRIPTION OF DRAWINGS

Features of the present disclosure are illustrated by way of example andnot limited in the following figure(s), in which like numerals indicatelike elements, in which:

FIG. 1A illustrates an operational layout of a fiber optic cablelocation system in accordance with an example of the present disclosure;

FIG. 1B illustrates acoustic signal amplitude measurement to illustrateoperation of the fiber optic cable location system of FIG. 1 inaccordance with an example of the present disclosure;

FIG. 2 illustrates further details of acoustic signal amplitudemeasurement to illustrate operation of the fiber optic cable locationsystem of FIG. 1 in accordance with an example of the presentdisclosure;

FIG. 3 illustrates details of components of the fiber optic cablelocation system of FIG. 1 in accordance with an example of the presentdisclosure;

FIG. 4 illustrates a flowchart of an example method for fiber opticcable location determination in accordance with an example of thepresent disclosure; and

FIG. 5 illustrates a computer system, according to an example of thepresent disclosure.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the present disclosure isdescribed by referring mainly to examples. In the following description,numerous specific details are set forth in order to provide a thoroughunderstanding of the present disclosure. It will be readily apparenthowever, that the present disclosure may be practiced without limitationto these specific details. In other instances, some methods andstructures have not been described in detail so as not to unnecessarilyobscure the present disclosure.

Throughout the present disclosure, the terms “a” and “an” are intendedto denote at least one of a particular element. As used herein, the term“includes” means includes but not limited to, the term “including” meansincluding but not limited to. The term “based on” means based at leastin part on.

Fiber optic cable location systems and methods for fiber optic cablelocation determination are disclosed herein. The systems and methodsdisclosed herein provide for implementation of a signal analyzer and amobile signal generator to locate buried nonmetallic cables, such asfiber-optic cables.

With respect to location of buried cables, a conductive component of acable may be utilized as an antenna to detect the cable. In this regard,inductive or capacitive coupling may be utilized to detect the cablelocation for cables that include, for example, a metallic wire embeddedin the cable or in a vicinity of the cable. For cables that do notinclude such conductive components, it is technically challenging todetect such cables, for example, when such cables are buriedunderground.

The systems and methods disclosed herein address at least theaforementioned technical challenges by utilizing a signal analyzer,which is operatively connected to a device under test (DUT) that mayinclude a fiber optic cable, to transmit a coherent laser pulse into theDUT. The signal analyzer may determine, based on an analysis ofreflected light resulting from the transmitted coherent laser pulse,changes in intensity of the reflected light caused by a plurality ofsignals generated by a mobile signal generator. The signal generator mayfurther transmit, to the mobile signal generator, the changes inintensity of the reflected light to determine a location of the DUT.

According to examples disclosed herein, the systems and methodsdisclosed herein may be utilized to locate any type of DUT that includesa minimum of a single mode fiber, such as a telecom fiber-optic cable,hybrid copper/fiber cables, sensing cables, a distributed temperaturesensing (DTS) monitored power cable, a pipeline with an optical fiber,etc.

FIG. 1A illustrates an operational layout of a fiber optic cablelocation system (hereinafter also referred to as “system 100”) inaccordance with an example of the present disclosure. Further, FIG. 1Billustrates acoustic signal amplitude measurement to illustrateoperation of the system 100 in accordance with an example of the presentdisclosure.

Referring to FIG. 1A, the system 100 may include a signal analyzer 102operatively connected to a device under test (DUT) 104 to transmit acoherent laser pulse (not shown) into the DUT 104. The signal analyzer102 may determine, based on an analysis of reflected light resultingfrom the transmitted coherent laser pulse, changes in intensity of thereflected light caused by a plurality of signals 106 (or a signal)generated by a mobile signal generator 108. In this regard, the mobilesignal generator 108 may generate the plurality of signals 106 in avicinity of the DUT 104. Further, the signal analyzer 102 may transmit,to the mobile signal generator 108, the changes in intensity of thereflected light to determine a location of the DUT 104.

According to examples disclosed herein, the DUT 104 may include a fiberoptic cable. In this regard, the DUT 104 may be disposed underground ormay be disposed above ground.

According to examples disclosed herein, the plurality of signals 106generated by the mobile signal generator 108 may include sound,vibration, and other such signals.

According to examples disclosed herein, the signal analyzer 102 maydetermine, based on the analysis of reflected light resulting from thetransmitted coherent laser pulse, changes in intensity of the reflectedlight caused by the plurality of signals 106 generated by the mobilesignal generator 108 by determining, based on the analysis of reflectedlight using coherent Rayleigh optical domain reflectometry, changes inintensity of the reflected light caused by the plurality of signals 106generated by the mobile signal generator 108.

According to examples disclosed herein, the signal analyzer 102 maytransmit the coherent laser pulse into the DUT 104 at a wavelength thatis different from a wavelength range of traffic associated with the DUT.In this regard, optical filtering may be utilized to avoid interferencebetween a wavelength of the coherent light pulse and wavelength(s) oftraffic associated with the DUT. For example, the system 100 may utilizewavelength division multiplexing to monitor the DUT 104 with a signalpropagating therein. For example, the coherent laser pulse may begenerated at 1625 nm, whereas traffic wavelength associated with the DUT104 may be at 1550 nm.

According to examples disclosed herein, the signal analyzer 102 maytransmit, to the mobile signal generator 108, the changes in intensityof the reflected light to determine the location of the DUT 104 bytransmitting, to the mobile signal generator 108, the changes inintensity of the reflected light to determine, based on identificationof a maximum signal level (e.g., as disclosed herein with respect toFIG. 1B) of a frequency tone emerging from a noise background, thelocation of the DUT 104.

According to examples disclosed herein, the signal analyzer 102 maydetermine a time of flight value from a location (e.g., a location ofthe signal analyzer 102) associated with transmission of the coherentlaser pulse to the location of the DUT 104. Further, the signal analyzer102 may determine, based on the time of flight value, a length of theDUT 104. For example, the time of flight value may be analyzed relativeto a speed of light associated with the coherent laser pulse todetermine the length of the DUT 104. In this regard, the length of theDUT 104 may be measured to within a few meters to several kilometers,for example.

According to examples disclosed herein, the signal analyzer 102 maydetect a specified frequency tone associated with the plurality ofsignals 106 generated by the mobile signal generator 108. Further, thesignal analyzer 102 may determine, based on analysis of the specifiedfrequency tone, a message transmitted from the mobile signal generator108 to the signal analyzer. For example, by using acoustic frequencymodulation, a digital message may be transmitted from the mobile signalgenerator 108 to the signal analyzer 102, in a similar manner astransmission of information on a sound stimulus (e.g., sound frequency).For example, a specified frequency tone of xyz Hz, may represent amessage for the signal analyzer 102 to disconnect from the DUT 104 uponthe location of the DUT 104.

According to examples disclosed herein, the mobile signal generator 108may be disposed in an unmanned aerial vehicle, a terrestrial vehicle, oranother type of vehicle. In this regard, the mobile signal generator 108may determine, based on the plurality of signals 106 generated duringmovement of the unmanned aerial vehicle or the terrestrial vehicle,points along the location of the DUT 104. Further, the mobile signalgenerator 108 may trace, based on the determined points along thelocation of the DUT 104, a layout of the DUT 104. According to anotherexample, the unmanned aerial vehicle or the terrestrial vehicle may emita non-audible sound signal that locates the DUT 104, and may thenautomatically (e.g., without human intervention) follow the DUT 104along its length to trace a route of the DUT 104.

Operation of the system 100 is described in further detail withreference to FIGS. 1A-2 .

Referring to FIG. 1A, the signal analyzer 102, which may also bereferred to as a distributed acoustic or vibration signal measurement(DAVSM) device, may analyze the acoustic signals along the length of theDUT 104. The mobile signal generator 108, which may also be referred toas a mobile acoustic signal generator, may be moved at the surface ofthe ground 110 near the buried DUT 104 and generate the plurality ofsignals 106, which may also be referred to as acoustic referencesignals. The signal analyzer 102 may detect the characteristic signalsof the mobile signal generator 108 that reach the DUT 104, and maytransmit this information to a user (not shown) of the mobile signalgenerator 108. Alternatively or additionally, the signal analyzer 102may transmit the information to a user of the signal analyzer 102 (orthe mobile signal generator 108) through, for example, a mobile deviceand an application. Thus, a user of the mobile signal generator 108 maymove the mobile signal generator 108 to locate the DUT 104 by lookingfor a maximum signal level 112 (e.g., at the optimal distance dopt) asshown in FIG. 1B. The maximum signal level 112 may represent a frequencytone of interest emerging from the noise background 114. In this regard,a user may trace a path of the plurality of signals 106 to follow theDUT 104 being located.

The mobile signal generator 108 may generate the plurality of signals106, which may be referred to as a stimulus, that radiate away from asurface of contact of the mobile signal generator 108 with the ground,and towards the DUT 104. Alternatively, the mobile signal generator 108may be disposed at a specified distance away from the surface of theground. In this regard, different acoustic frequencies (e.g., tones) maybe used to account for aspects such as different soil composition,types, and/or configuration of the buried DUT 104. The acousticpropagation properties of soil may be a function of factors such as soilmoisture, composition, etc. Short frequencies may be used to reduce soilattenuation, but some components of the soil may impact the soundpropagation (e.g., sound reflection).

The signal analyzer 102 may communicate with the mobile signal generator108, for example, by a wireless connection 116, or by other transmissionmeans that provides acceptable latency for real-time communicationbetween the signal analyzer 102 and the mobile signal generator 108.

As disclosed herein, the signal analyzer 102 may determine, based on theanalysis of reflected light using coherent Rayleigh optical domainreflectometry, changes in intensity of the reflected light caused by theplurality of signals 106 generated by the mobile signal generator 108.In this regard, the Rayleigh reflectometry based solution provided bythe system 100 may provide positioning information on any buried (orunburied) DUT 104, irrespective of whether the DUT 104 includes aconductive component that may be utilized as an antenna to detect theDUT 104.

With respect to the Rayleigh reflectometry based detection of theplurality of signals 106 generated by the mobile signal generator 108,as disclosed herein, the signal analyzer 102 may transmit a coherentlaser pulse into the DUT 104. In this regard, various scattering sitesalong the DUT 104 may cause the DUT 104 to act as a distributedinterferometer. The intensity of the reflected light resulting from thecoherent laser pulse may be measured as a function of time after thetransmission of the coherent laser pulse. In this regard, a sound orvibration transmitted to the DUT 104 (e.g., from the plurality ofsignals 106) may be seen as a signal emerging from the noise background114.

For example, FIG. 2 illustrates further details of acoustic signalamplitude measurement to illustrate operation of the system 100 inaccordance with an example of the present disclosure.

Referring to FIG. 2 , with respect to the Rayleigh reflectometry baseddetection of the plurality of signals 106 generated by the mobile signalgenerator 108, when an optical signal propagates along an optical fiber,an elastic diffusion called Rayleigh scattering may be generated. TheRayleigh scattering signal may occur due to microscopic variations inthe density of the optical fiber (e.g., micro-scattering centers).Rayleigh backscatter based optical time-domain reflectometers (OTDRs)may utilize this phenomena in telecommunications. Coherent fading noisemay appear on OTDR traces as additional noise that may not be removedwith averaging. Different techniques may be used to reduce thisphenomena in order to increase signal to noise ratio. One such techniquemay include the use of low coherence optical sources to smooth thiseffect. Alternatively, distributed acoustic sensing (DAS) opticalsources may include a relatively long coherence length that may lead toa high coherent fading noise. Under such conditions, an acoustic wavereaching the optical fiber may modify the phases of signal from the backscattering centers, and may thus modify the shape of the coherencenoise. By analyzing the local variation of amplitude and possibly phaseof this noise on successive traces, the signals 106 (e.g., which mayinclude an acoustic wave), and also an associated amplitude andfrequency content may be detected. The acoustic signal activity may beanalyzed all along the length of the DUT 104. When analyzing severalsuccessive traces, sections of the DUT 104 impacted by the signals 106may show amplitude and phase variation, whereas other sections may showa repeatable noise pattern. When translated in acoustic signalamplitude, the analysis of the noise background 114 (e.g., thedistributed acoustic signal) may show the section of the DUT 104impacted by a sound stimulus due to coherent noise variation.

As shown in FIG. 2 , at 200, multiple successive traces may be acquiredby the signal analyzer 102. The DUT segment stimulated by the signals106 may be at distance d2, and the impact on the traces may be bound bythe dotted line area 202. Inside the area impacted by the signals 106,the noise pattern may change from trace to trace, while outside thisarea the noise pattern may be relatively stable. The curves 204 (e.g.,at d1), 206 (e.g., at d3), and 208 (e.g., at d2) may show variations ofnoise amplitude at a defined location from successive traces.

Outside of the acoustic stimulated area, the noise pattern may berelatively stable in shape leading to relatively low variation fromtrace to trace. In these areas, the sound related signal at curves 204and 206 may be relatively lower compared to the sound related signal atcurve 208 in the acoustically stimulated area where the noise changes inphase and amplitude. The signal at curve 208 may be analyzed to detectamplitude, and possibly the acoustic spectral content. If the soundstimulus is based on defined characteristics such as reference soundfrequencies or tones, the analysis of the spectral content mayfacilitate location of the optical fiber section of interest around d2.The sound sampling frequency may depend on the rate of successive traceacquisitions that depends on the DUT length. In such conditions, alength of the DUT may be inversely proportional to the acousticbandwidth.

The mobile signal generator 108 may include a visual and/or headsettracking system to locate the DUT 104. In this regard, the visualdisplay of FIG. 1B may alternatively be provided in a bar graph, orvariable frequency format to locate the DUT 104.

FIG. 3 illustrates details of components of the system 100 in accordancewith an example of the present disclosure.

Referring to FIG. 3 , the signal analyzer 102 may be operativelyconnected to the DUT 104 to transmit a coherent laser pulse into the DUT104. A processing unit 300 may analyze the acoustic data generated bythe mobile signal generator 108 on the DUT 104. The processing unit 300may use a communication interface 302 to send information through acommunication link 304 to a communication interface 306 of the mobilesignal generator 108. The processing unit 308 of the mobile signalgenerator 108 may receive the sound information from the communicationinterface 306, and convert this sound information to an indication to auser regarding the proximity of the DUT 104.

FIG. 4 illustrate a flowchart of a method 400 for fiber optic cablelocation determination, according to examples. The method 400 may beimplemented on the signal analyzer 102 and/or the mobile signalgenerator 108 described above with reference to FIGS. 1A-2 by way ofexample and not limitation. The method 400 may be practiced in othersystems.

Referring to FIGS. 1A-4 , and particularly FIG. 4 , at block 402, themethod 400 may include transmitting a coherent laser pulse into a DUT104.

At block 404, the method 400 may include determining, based on ananalysis of reflected light resulting from the transmitted coherentlaser pulse, changes in intensity of the reflected light caused by aplurality of signals directed towards the DUT 104.

At block 406, the method 400 may include determining, based on thechanges in intensity of the reflected light, a location of the DUT 104.

FIG. 5 shows a computer system 500 that may be used with the examplesdescribed herein. The computer system may represent a platform thatincludes components that may be in a server or another computer system.The computer system 500 may be used as part of a platform forcontrollers of the signal analyzer 102 and/or the mobile signalgenerator 108 (generally designated controller). The computer system 500may execute, by a processor (e.g., a single or multiple processors) orother hardware processing circuit, the methods, functions and otherprocesses described herein. These methods, functions and other processesmay be embodied as machine readable instructions stored on a computerreadable medium, which may be non-transitory, such as hardware storagedevices (e.g., RAM (random access memory), ROM (read only memory), EPROM(erasable, programmable ROM), EEPROM (electrically erasable,programmable ROM), hard drives, and flash memory).

The computer system 500 may include a processor 502 that may implementor execute machine readable instructions performing some or all of themethods, functions and other processes described herein. Commands anddata from the processor 502 may be communicated over a communication bus504. The computer system may also include a main memory 506, such as arandom access memory (RAM), where the machine readable instructions anddata for the processor 502 may reside during runtime, and a secondarydata storage 508, which may be non-volatile and stores machine readableinstructions and data. The memory and data storage are examples ofcomputer readable mediums. The main memory 506 may include thecontroller (e.g., for the signal analyzer 102 and/or the mobile signalgenerator 108) including machine readable instructions residing in themain memory 506 during runtime and executed by the processor 502.

The computer system 500 may include an input/output (I/O) device 510,such as a keyboard, a mouse, a display, etc. The computer system mayinclude a network interface 512 for connecting to a network. Other knownelectronic components may be added or substituted in the computersystem.

The processor 502 may be designated as a hardware processor. Theprocessor 502 may execute operations associated with various componentsof the signal analyzer 102 and/or the mobile signal generator 108. Forexample, the processor 502 may execute operations associated with thecontroller (e.g., for the signal analyzer 102 and/or the mobile signalgenerator 108), etc.

What has been described and illustrated herein is an example along withsome of its variations. The terms, descriptions and figures used hereinare set forth by way of illustration only and are not meant aslimitations. Many variations are possible within the spirit and scope ofthe subject matter, which is intended to be defined by the followingclaims—and their equivalents—in which all terms are meant in theirbroadest reasonable sense unless otherwise indicated.

What is claimed is:
 1. A fiber optic cable location system comprising: asignal analyzer operatively connected to a device under test (DUT) to:transmit a coherent laser pulse into the DUT; receive, from the DUT,reflected light resulting from the transmitted coherent laser pulse;determine, based on an analysis of the reflected light, changes inintensity of the reflected light caused by a plurality of vibrationalsignals generated by a mobile signal generator and directed towards anarea where a location of a section of the DUT is to be determined; andtransmit, to the mobile signal generator, the changes in intensity ofthe reflected light by which the mobile signal generator determines thelocation of the section of the DUT.
 2. The fiber optic cable locationsystem according to claim 1, wherein the signal analyzer is todetermine, based on the analysis of reflected light, changes inintensity of the reflected light caused by the plurality of vibrationalsignals generated by the mobile signal generator and directed towardsthe area where the location of the section of the DUT is to bedetermined by: determining, based on the analysis of reflected lightusing coherent Rayleigh optical domain reflectometry, changes inintensity of the reflected light caused by the plurality of vibrationalsignals generated by the mobile signal generator and directed towardsthe area where the location of the section of the DUT is to bedetermined.
 3. The fiber optic cable location system according to claim1, wherein the signal analyzer is to transmit the coherent laser pulseinto the DUT at a wavelength that is different from a wavelength rangeof traffic associated with the DUT.
 4. The fiber optic cable locationsystem according to claim 1, wherein the DUT includes a fiber opticcable.
 5. The fiber optic cable location system according to claim 1,wherein the DUT includes a fiber optic cable that is disposedunderground.
 6. The fiber optic cable location system according to claim1, wherein the DUT includes a fiber optic cable that is disposed aboveground.
 7. The fiber optic cable location system according to claim 1,wherein the plurality of vibrational signals generated by the mobilesignal generator includes sound.
 8. The fiber optic cable locationsystem according to claim 1, wherein the signal analyzer is to:determine a time of flight value from a location associated withtransmission of the coherent laser pulse to the location of the DUT; anddetermine, based on the time of flight value, a length of the DUT. 9.The fiber optic cable location system according to claim 1, wherein thesignal analyzer is to: detect a specified frequency tone associated withthe plurality of vibrational signals generated by the mobile signalgenerator; and determine, based on analysis of the specified frequencytone, a message transmitted from the mobile signal generator to thesignal analyzer.
 10. The fiber optic cable location system according toclaim 1, wherein the location of the section of the DUT is determinedbased on noise variation over time of the changes in intensity caused bythe plurality of vibrational signals generated by the mobile signalgenerator.
 11. A fiber optic cable location system comprising: a mobilesignal generator to: generate a plurality of vibrational signalsdirected towards an area where a location of a section of a device undertest (DUT) is to be determined; receive, from a signal analyzer that isoperatively connected to the DUT to transmit a coherent laser pulse intothe DUT, an indication of changes in intensity of reflected lightresulting from the transmitted coherent laser pulse and caused by theplurality of vibrational signals generated by the mobile signalgenerator and directed towards an area where a location of a section ofthe DUT is to be determined; and determine, based on the changes inintensity of the reflected light, the location of the section of theDUT.
 12. The fiber optic cable location system according to claim 11,wherein the DUT includes a fiber optic cable.
 13. The fiber optic cablelocation system according to claim 11, wherein the plurality of thevibrational signals generated by the mobile signal generator includessound.
 14. The fiber optic cable location system according to claim 11,wherein the mobile signal generator is to determine the location of thesection of the DUT based on noise variation over time of the changes inintensity caused by the plurality of vibrational signals generated bythe mobile signal generator.
 15. The fiber optic cable location systemaccording to claim 11, wherein the mobile signal generator is togenerate an indication of a proximity to the mobile signal generator ofthe location of the section of the DUT.
 16. A fiber optic cable locationdetermination method comprising: transmitting a coherent laser pulseinto a device under test (DUT); receiving, from the DUT, reflected lightresulting from the transmitted coherent laser pulse; determining, basedon an analysis of the reflected light, changes in intensity of thereflected light caused by a plurality of vibrational signals generatedby a mobile signal generator and directed towards an area where alocation of a section of the DUT is to be determined; and transmitting,to the mobile signal generator, the changes in intensity of thereflected light, to determine the location of the section of the DUT.17. The fiber optic cable location determination method according toclaim 16, wherein determining, based on the analysis of the reflectedlight, changes in intensity of the reflected light caused by theplurality of vibrational signals directed towards the area where thelocation of the section of the DUT is to be determined, furthercomprises: determining, based on the analysis of the reflected lightusing coherent Rayleigh optical domain reflectometry, changes inintensity of the reflected light caused by the plurality of vibrationalsignals directed towards the area where the location of the section ofthe DUT is to be determined.
 18. The fiber optic cable locationdetermination method according to claim 16, wherein transmitting thecoherent laser pulse into the DUT further comprises: transmitting thecoherent laser pulse into the DUT at a wavelength that is different froma wavelength range of traffic associated with the DUT.
 19. The fiberoptic cable location determination method according to claim 16, whereinthe DUT includes a fiber optic cable.
 20. The fiber optic cable locationdetermination method according to claim 16, further comprising:determining a time of flight value from a location associated withtransmission of the coherent laser pulse to the location of the DUT; anddetermining, based on the time of flight value, a length of the DUT.